One of Metcash's largest customers, Drakes Supermarkets, plans to go into competition with the $2.7 billion wholesaler by supplying other independent supermarkets.

Drakes, which turns over more than $1 billion in annual sales and buys $270 million of food and groceries a year from Metcash, is moving to self-supply in South Australia next month after opening its own $125 million state-of-the-art automated distribution centre.